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Linear skull fractures, the most common type of skull fracture, occur in 69% of patients with severe head injury.[3][2] Usually caused by widely distributed forces, linear fractures often occur when the impact causes the area of the skull that was struck to bend inward, making the area around it buckle outward.[3][2]

In rare cases, a linear fracture can develop and lengthen as the brain swells, in what is called a growing fracture. This can cause growth of cysts in the meninges.[2][4]Diastatic fractures are linear fractures that cause the bones of the skull to separate at the skull sutures in young children whose skull bones have not yet fused.[5] Orlando Regional Healthcare, 2004). They are usually caused by impact with a wide area such as a wall.[3]

Comminuted skull fractures, those in which a bone is shattered into many pieces, can result in bits of bone being driven into the brain, lacerating it.[3]Depressed skull fractures, a very serious type of trauma occurring in 11% of severe head injuries, are comminuted fractures in which broken bones are displaced inward.[2] This type of fracture carries a high risk of increasing pressure on the brain, crushing the delicate tissue. Complex depressed fractures are those in which the dura mater is torn. Depressed skull fractures may require surgery to lift the bones off of the brain if they are causing pressure on it.[1]

Basilar skull fractures, breaks in bones at the base of the skull, require more force to cause than cranial vault fractures. Thus they are rare, occurring as the only fracture in only 4% of severe head injury patients.[2][4] Basilar fractures have characteristic signs: blood in the sinuses; a clear fluid called cerebrospinal fluid (CSF) leaking from the nose or ears; raccoon eyes (bruising of the orbits of the eyes that result from blood collecting there as it leaks from the fracture site); and Battle's sign (caused when blood collects behind the ears and causes bruising).